Benzoxazines are a class of thermoset materials that are useful in the fabrication of electronic devices and other composites. Benzoxazines can undergo thermal curing with or without a curing catalyst to form polybenzoxazines. Relative to epoxy thermosets, benzoxazines typically cure at lower temperatures and do not require curing catalysts or hardening agents. Cured thermosets derived from benzoxazines also absorb much less moisture than those derived from epoxies. Benzoxazines also demonstrate near-zero shrinkage during curing (which is a significant improvement from epoxy resins), and no volatiles are released during curing reactions. Polybenzoxazines offer a low melt viscosity, high glass transition temperature, high thermal stability, good mechanical strength, low dielectric constant and good resistance to burning. In addition, the cure exotherms for benzoxazines are much lower than those of epoxies, thereby allowing fabrication of thicker sections, longer injection times, and larger parts.
Compounds containing two benzoxazine groups (i.e., bis(benzoxazinyl) compounds) are known. See, for example, U.S. Patent Application No. US 2011/0152453 A1 of Tietze et al., which describes bis(benzoxazinyl) derivatives of phenolphthalein. However, there is a desire for bis(benzoxazinyl) compounds exhibiting higher melting temperatures and higher exotherm onset temperatures.